1. Field of the Invention
The present invention generally relates to pipeline inspection methods and apparatus therefor, and particularly to a pipeline inspection gauge (PIG) alert system for determining the presence and location of a pipeline inspection gauge (PIG) within a pipeline.
2. Description of the Related Art
The use of pipelines to convey liquid, semi-liquid, and gaseous products is commonplace in the industrial world. Pipelines are employed to convey products as diverse as crude oil, paints, liquid cosmetics, liquid foodstuffs, natural gas and the like. The integrity of the pipeline is vital to the conveying process. The disruption of flow caused by a ruptured or clogged pipeline can result in extensive monetary losses and may pose a danger to property and human life. Thus, the pipeline requires periodic inspection and cleaning to ensure that integrity is maintained.
In the context of pipelines, “pigging” refers to the practice of employing a pipeline inspection gauge (PIG) to perform the inspection and/or cleaning tasks necessary to maintain the integrity of the pipeline. The PIG can be fitted with scrapers and brushes to clean the inner walls of the pipeline and/or provided with electronic sensors to determine pipe thickness and corrosion areas along the pipeline. The PIG does not disrupt the product flow in the pipeline. The flow propels the PIG along the pipeline. Usually a PIG is inserted in the pipeline at a launching station and retrieved at a receiving station. There may be several launching and retrieving stations spaced along the length of a pipeline. It is important in the procedure to determine if the PIG has been successfully launched and when the PIG arrives at a receiving station. In oil and natural gas pipelines this determination has required the manipulation of heavy gates, which makes for a time-consuming and inefficient process procedure in locating the PIG. Alternatively, expensive and delicate electronic apparatus has been applied to determine the location of the PIG in the pipeline. The industry would certainly embrace an inexpensive and reliable procedure and apparatus for locating a PIG as it proceeds through the pipeline. Thus, a pipeline inspection gauge alert system solving the aforementioned problems is desired.